Surface coating with metallic powder and the like



April 9, 1963 M. S. EATON SURFACE COATING WITH METALLIC POWDER AND THELIKE Filed Sept. 14, 1959 SUBSTRATE OR THERMOPLASTIC BODY SURFACE OF AHOT M ELT COAT APPLY GLOSSY THERMOPLASTIC FILM SUBSTRATE WITH THERMO-PLASTIC FILM AND DRAW UNDER TENSION ACROSS SURFACING BAR IMPARTDECORATIVE DESIGN TO FILM PARTICULATE MATTER TO FILM IN NORMAL,NON-TACKY STATE APPLY FINELY DIVIDED RECONVERT FILM TO NORMAL, NON-TACKY STATE MODIFIED SURFACE INVENTOR.

Mark S. Eaton Attorney United States Patent 3,085,025 SURFACE CQATENGWITH METALLIC PGWDER AND THE LIKE Mark S. Eaton, Littleton, Mam,assignor to Arthur D.

Little, Inc., Cambridge, Mass, a corporation of Massachusetts FiledSept. 14, 1959, Ser. No. 839,582 9 Claims. (Cl. 117-9) This inventionrelates to coated surfaces and a process for forming them and moreparticularly to metalized surfaces.

Heretofore metalized articles and particularly metalized packagingmaterials have been produced by laminating a suitably-surfaced metallicfoil to a base material, such as paper. While this type of product hasbeen satisfactory for many applications it is relatively expensive tomake, and if it is desired to incorporate color into the surface, it isnecessary to introduce additional processing steps in the coloringoperation.

It has also been proposed in the prior art to form metalized surfaces,and particularly metalized papers, by coating the surface with metallicpowders or with so-called metallic leafing pigments suspended in aliquid, or by permitting metallic powders or leafing pigments to settleinto a liquid binder deposited on the articles surface. Many of theseprocesses require bufiing, powder or pigment alignment, or other stepsto impart the necessary luster to the finished surface. Such metalizedpapers may be subject to severe cracking when bent or folded dueapparently to the nature of the metalized surface. Moreever, the amountof metal powder required to fill the liquid is relatively high thusmaking a heavy coating. It

is not believed that any of the processes involving the combination of ametal powder in a liquid has resulted in commercially acceptableproducts, particularly for decorative wrappings and packaging.

A more recently developed technique involves the direct application of ametallic coating by means of Well-known vacuum deposition techniques.The process is expensive and does not lend itself to a continuouscoating operation because of the requirement for a vacuum.

From the above description of the prior art it may be seen that each ofthe processes of the prior art for metalizing a surface suffers from oneor more defects. Among these defects may be listed the requirement for alarge number of process steps, the use of a relatively large amount ofmetal powder, the use of expansive equipment, the difficulty of adaptingthe process to continuous operation and the difficulty of forming asurface which is not susceptible to cracking when bent or creased.

There exists a large demand in the decorative wrapping field, in thefield of packaging small articles and food, particularly bread and thelike, and in the field of thermal insulation for a metalized flexibleproduct which can be handled, printed on, sealed and otherwise employedwithout cracking or affecting the general appearance of the metalizedproduct. Such a metalized product should be inexpensive, pleasing to theeye, and of such a nature that it can easily be varied in appearance,e.g., colored, stippled, striated, and the like. Moreover, it shouldadhere well to the substrate on which it is deposited, be flexible andcapable of being bent, folded and creased, without exhibiting anyappreciable undesirable markings and preferably, for some applications,without showing any appreciable increase in moisture vapor or gaseoustransmission. -For some applications it would also be desirable to havea metalized wrapping paper which has other properties such as beingheat-scalable, grease-resistant and the like. Finally, it would bedesirable to have a process which permits using a wide range of metalpowders or other suitable particulate matter over a wide range of "icepowder pick-up to produce metalized articles having a Wide range ofproperties.

It is, therefore, the principal object of the present invention toprovide attractive metalized articles which are inexpensive, which arereadily provided with various surface appearances including a variety ofcolors, and which may possess other properties such as beingheat-sealable, grease-resistant or vapor-resistant. Another object is toprovide articles of the character described wherein the metallic surfaceis permanently afiixed and not subject to scarring or marking by areasonable amount of pressure. Another object is to provide a metalizedpaper which is flexible and which may be folded and creased withoutcracking the metalized portion.

:It is yet another object to provide a rapid method for metalizing thesurface of articles which achieves an attractive lustrous surface with aminimum amount of a metallic powder. It is still another object toprovide a process by which colored metallic surfaces may be achievedwithout additional processing steps. Other and further objects of theinvention will be apparent from the following description.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the single FIGURE, which is a simplified flow diagram ofthe method of the invention.

In accordance with this invention these objects are achieved by applyingto the surface of an article an essentially continuous glossy film of athermoplastic material as a binder, applying to said film finely dividedparticulate matter sufficient to cover at least 10% of the surface ofsaid film, and converting the surface of said film by heat to a viscousliquid supporting said matter in substantially the outer surface thereofwhereby said matter is supported by said surface and firmly bondedthereto to produce an attractive surface. Color can be introduced by theuse of colored film or by the use of colored particulate matter,preferably comprising a metallic powder. if the article to be surfacecoated has a surface of a suitable thermoplastic material, theparticulate matter can, of course, be applied directly to the surface ofthe article.

By the process of this invention attractive finishes varying from ahighly lustrous metallic surface suitable for decorative purposes to arich matte appearance can be provided without polishing or bufiing thesurface, without requiring the alignment of the particles of powder, orwithout additional steps to introduce a variety of coloring matter. Theamount of powder deposited may vary over a wide range as describedbelow, thus giving the metalized article a very wide range ofproperties.

In order to make a metalized article and particularly a metaliz'ed sheetof paper suitable for such uses as food and small article pack-aging,decorative wrappings and the like, it has been found necessary to use athermoplastic material, in the role of a binder film or coating, whichis both tough and flexible. Thus, the material should be of a fairlyhigh molecular weight to give the toughness required, and preferablyhave a measurable tensile strength and also preferably a measurabledegree of elongation.

Since the actual molecular Weight of film forming materials having thedesired degree of toughness will vary from material to material, andmoreover, since molecular weight is not easily determined, toughness forthe purpose of this invention is defined in terms of viscosity of thethermoplastic film material at a given temperature. The temperaturechosen to evaluate the film binder required for the practice of thisinvention is 300 F. and a thermoplastic material to be suitable for thebonding film between the substrate surface and the metal powder shouldhave a viscosity of at least 1000 centipoises at 300 F. Brookfield, 20rpm. spindle speed.) It is preferable, however, that the thermoplasticmaterial have a viscosity of at least 3000 centipoises at 300 F., sincethe higher viscosity material gives a better metalized coating. Therequirement for high viscosity at elevated temperatures is also dictatedby the fact that when the film is heated to bond the metal powder, thefilm must support the powder to prevent any appreciable penetration ofthe power into the film.

The property of flexibility can be related to tensile strength and tosome extent to degree of elongation of the film-forming thermoplasticmaterial. The thermoplastic binder of this invention is furtherdescribed as one having a measurable tensile strength, i.e., at leastabout 100 psi. as measured by the procedure set forth in ASTM TestD-88249T. A preferable tensile strength may be defined as 1000 p.s.i. orgreater.

Although thermoplastic binders having little if any degree of elongationhave been found to be satisfactory, it is preferable to usethermoplastic materials having at least a measurable degree ofelongation, e.g., at least about to A thermoplastic binder materialshould also possess other general characteristics, among which may belisted the ability to be applied as a continuous film in a highly glossystate. It will be shown in the description below that the gloss of thefinal metalized surface is related to the degree of glossiness of theoriginal film binder as it is applied to the substrate surface.Furthermore, the thermoplastic binder should be a material which can beapplied to adhere well to the substrate.

The thermoplastic binder may also possess additional desirablecharacteristics which make the finished decorative article andparticularly metalized paper suitable for a number of applications.These additional characteristics which can be achieved include, but arenot limited to, ability to be colored, low moisture vapor transmission,low gas permeability, resistance to grease, heat-scalable, and easilydeposited in the form of a thin film on the substrate. It will beapparent to those skilled in the art that by the proper choice of thethermoplastic binder the final metalized article may be given desiredand predetermined physical characteristics. For example, the use of apolyethylene film results in the production of a heat-scalable paperwhich exhibits very low moisture vapor transmission and which has a goodtensile strength and hence makes a good metalized paper for foodwrappings.

The thermoplastic binder can also contain modifiers known to give thethermoplastic film certain desired characteristics. For example, theymay contain tackifiers, plasticizers, and the like. These will bemodifiers which are commonly employed with the various thermoplasticfilms and known to those familiar with plastic formulation techniques.

In the practice of this invention a wide variety of thermoplasticmaterials have been found suitable which possess the characteristics setforth for the film. Among the thermoplastic materials which can beemployed in the practice of this invention are polyethylene, acrylics,polyamides, polyvinyl butyrals, polyvinyl formals, polyvinyl acetatesand their copolymers with vinyl chloride, ethyl cellulose, styrene andits copolymers with butadiene and the like.

There are known in the art a number of Ways of applying 'thin films ofthese thermoplastic binder materials to the surface of a substrate. Suchmethods include hot melt coating, calendering, extruding, and coatingfrom a solvent or dispersion. The term coating as herein used inreferring to the film of thermoplastic binder material on the substrateincludes films applied by any of these methods as well as other knownmeans of application. The type of binder film selected will depend onthe intended end use, the particular binder being applied to thesubstrate by a method known to be appropriate for that material.

It has been found that the gloss of the finished metalized article isdirectly related to the degree of glossiness of the thermoplastic filmbinder originally deposited on the surface. There are a number of waysknown in the art for depositing thin films of these thermoplasticmaterials having varying degrees of gloss. For example, if thethermoplastic material is to be deposited as a hot melt coating, thecoated substrate can be run over a hot smoothing bar while the film isstill in a melted condition to obtain high gloss. Other techniques forforming a glossy film include but are not limited to calendering, rapidchilling and the like. The choice of binder material also affects thefinal degree of gloss obtainable. Degree of gloss is readily andconventionally determined by visual means.

The thickness of the film on the surface is not critical as long as itis essentially a continuous film and preferably without substrateparticles projecting therethrough. For example, films of thicknesses nogreater than one-tenth mil are satisfactory provided they can bedeposited upon the surfaces economically. Although films are normallydefined as having thicknesses up to about 10 mils, this need not beconsidered an upper limit. However, for practical reasons, films rangingfrom about one-half to 2 mils thick {have been found to be verysatisfactory. Generally where flexibility of the finished metalizedarticle is important, it will be desirable to use thinner films.

Any metal powder which can be reduced to an extremely fine form issuitable for the practice of this invention. Among such metal powdersare aluminum, cop per, bronze, zinc, combinations of these and the like.Very finely divided particulate matter such as a ultramarine blue,commonly used as a pigment in paints, can also be used. The metallicpowders or other particulate matter should be very finely divided,preferably about 325-mesh or finer. Although the generic term powder hasbeen used to define the particulate matter, it is possible also to usewhat is referred to as a leafing pigment, the latter usually having astearic acid coating. However, it has been found that uncoated powder ofthe dimensions specified is preferable.

As noted above, other finely divided particulate matter meeting the sizespecification set forth may be substituted for the metallic powder ormay be combined with metallic powder. For example, finely dividedcoloring material such as ultramarine blue can be added to the metallicpowder.

The amount of powder deposited and remaining adhered to the film bindercan be varied over a wide range depending upon the use to which themetalized article is to be put. Assuming for example that a paper is tobe metalized, it has been found that as little as 10% of thethermoplastic film surface need be covered with metal powder to give ametalized surface which is extremely lustrous and attractive to the eye.It is preferable, however, in applications where the paper is to serveprimarily in a decorative role, that from 20 to 40% of the film surfacebe covered in substantially uniform distribution with the metallicpowder, thereby exposing in the finished article a major portion of thethermoplastic surface.

If the paper or metalized article is to serve as a thermal barrier orheat insulating material it is preferable that at least 75% of thesurface of the binder film be covered with the metal powder and evenmore preferable if this approaches or actually attains This has beendemonstrated in a simple experiment in which metalized paper formed inaccordance with the process of this invention was evaluated for itsability to act as a heat barrier. A piece of thermal paper treated toturn black at 200 F. was taped to the under side, i.e., unmetalizedside, of a sample of metalized paper and the corresponding metalizedsurface was exposed to radiation from a 375-watt infrared lamp placed 8inches above the metalized surface. When a metalized paper having aboutof its area actually covered with aluminum powder was exposed toradiation, the thermal paper turned black in less than 10 seconds. Whena metalized paper, the area of which was about 80% covered with aluminumpowder, was tested in the same manner, the thermal paper did not turnafter three minutes of exposure.

It will be seen that by the process of this invention it is possible tomake a metalized article which is pleasing to look at and which containsa very small amount of, particulate matter adhered to a glossythermoplastic bonding film. For example, as little as one-quarter poundof aluminum per ream (3000 square feet) can be used. A preferable powderpick-up range is from about 0.25 to 0.5 pound per ream for decorativepaper. This, of course, can be higher for thermal insulation material asshown above, i.e., up to about 1 to 1.5 pounds.

The ability to make a metalized article the surface of which isextremely reflective and appealing to the eye with so little metalpowder is brought about through the practice of this invention by thefact that the metallic particles are deposited only upon the surface ofthe glossy thermoplastic bonding film and do not penetrate to anyappreciable extent into the film. This is to be distinguished overmetalized coatings which are applied either as a paint or by depositingmetal powder in a binder which is reduced to a free-flowing liquid.Moreover, by the process of this invention no additional steps such asbufiing or aligning of the metallicpowder are required. Thus, the finalmetalized article may be described as having from about 10 to 100% ofits surface area covered by metallic powder or other finely dividedparticulate matter.

As above described, the higher gloss of the thermoplastic film, the morelustrous the final metalized article. This is especially true of themetalized surfaces having the smaller area coverage with particulatematter. Apparently, even though the entire surface is not covered, thehuman eye integrates the entire surface to give a sensation of a highlypolished surface which is very pleasing.

After the thermoplastic binder has been applied in an essentiallycontinuous glossy film, the metallic powder or other finely dividedparticulate matter is deposited by any suitable way on the film surface.It can be dusted on, brushed on, or applied by any other suitabletechnique known in the art, including deposition in the form of adispersion. The dispersing medium in this latter case may be anon-solvent (e.g., water) or a solvent (e.g., organic liquid) for thethermoplastic binder film. The dispersion medium should, however, be aliquid which wets the thermoplastic film. If it is a solvent, it mayhelp bond the powder to the film but does not replace the next step ofheating the film.

This next step comprises converting, by heat, at least that portion ofthe surface of the binder film contacting the particulate matter to aviscous liquid capable of bonding the particulate matter to the surface.Thus it is necessary to render only the said portion of the outersurface of the film bendable to the powder. It is unimportant whether ornot the body of the film be melted provided its viscosity issufiiciently high to prevent settling or penetration of the particulatematter appreciably below the surface. For this reason, it is preferredthat the body of the binder have a viscosity (Brookfield at 20 rpm.spindle speed) during bonding of at least 3000-4000 centipoises.

The step of converting the film surface to a viscous liquid isaccomplished by heating the surface of the article, for example, byexposing the surface fora required period of time to a heatedatmosphere, or by heating the substrate. Thus it is possible toaccomplish this step of converting the surface to a viscous liquid byinfrared, induction or other known means of heating.

After the film surface has been converted to a viscous liquid and theindividual particles of metal or other particulate material have beenfirmly anchored to the surface of the film, the article is then cooled.In some cases it will be further desirable to accomplish the cooling asrapidly as possible to give higher gloss, depending upon thethermoplastic film binder and its characteristics. Rapid cooling orchilling can be accomplished by application of cold water, passing overa cold surface such as a drum and the like.

Further decorative effects can be achieved by imparting a design to thebinder while the binder is applied to the substrate. For example, thehot binder on the substrate can be drawn over a wire-wound surfacing barto impart an attractive ribbed appearance. The article can also beembossed before or after particulate matter is applied thereto, or theabove heat can be applied in a pattern.

Finally, in the process of this invention it may be necessary to removeany excess metallic particles or other particulate matter after coolingand solidifying of the film has been accomplished. This can be done byany suitable way, such as lightly brushing off the excess with sheepskin rolls for example, gently vibrating the metalized article to shakeloose the unattached particles or other similar techniques.

The particulate coating according to this invention can be applied tosubstantially any desired backing including wood, cloth, paper andcellophane. Expensive, high-grade papers are not required. In additionto sheet materials, the process can be used to metalize thread or moldedobjects economically. For example, nylon or rayon threads can be coatedwith the polyethylene melt of Example 1 below, cooled, dusted with metalpowder and heated to set, all as set forth in Example 1. If desired forimproved laundry and light-fastness characteristics, the metalizedthreads can thereafter be given a clear coating of plastic. Similarly,molded articles not already possessing the requisite surface can becoated, for example, with the polyethylene melt in Example 1, andthereafter rnetalized in a similar manner.

Further-more, the process of this invention can also be applied toarticles already posessing a suitable thermoplastic surface withoutadditional coating. Thus articles molded from resins as herein set forthcan be dusted with metal powder and fused as previously described toprovide an attractive metallic surface.

This invention is further described by the following examples which aremeant to be illustrative and not limiting. Since the metalizing of paperputs the most stringent requirements on the bonding film as far asflexibility and toughness are concerned, the thermoplastic film binderwill be discussed and defined in terms of its use on a paper surface.However, it is, of course, not meant to limit the substrate to paper,which is used hereinafter for purposes of illustration only.

Example 1 To a suitable base, for example an -pound paperboard (reambasis, 50020 by 26 inch sheets), a 0.6-mil coating of low-molecularweight polyethylene (Epolene C of Eastman Chemical Products, Inc.), wasapplied from a hot melt at 350 F. by roll coating. This lowmolecularWeight polyethylene is further characterized as having a melting pointof about C., an elongation of 50% to 60%, a tensile strength of 900 psi.and a Brookfield vis cosity of 8000 centipoises at 300 F. While thepolyethylene was still in a molten state, the paper was passed over ahot finishing roll to impart a high degree of glossiness to the filmthus formed.

After this binder film was cooled, a step which can include passing itover a chilled drum, finely divided aluminum powder was applied bydusting onto the coating face using sheepskin-covered rolls. Thealuminum powder applied was 325-mesh, non-leafing pigment (sold by theAluminum Company of America as Alcoa N 0. 552). The dusted film was thenheated in a circulating-air oven for one minute at 350 F. to convert thesurface to a highly viscous liquid without completely melting thecoating,

thereby firmly and attractively anchoring the metal powder to thecoating. The metal coating thus applied was very thin, covering about 25to 30% of the actual film surface as measured under a microscope andpresent in a weight equivalent to about 0.35 pound per ream. The resultwas a metalized surface with a rich brilliance having the aluminumpowder so firmly bonded to the coating that it would not rub-off to anysignificant extent.

The surface appearance of the article could be further enhanced, ifdesired, by rapidly chilling the same after fusion by passing the coatedface over a smooth, chilled roll or by applying cold water directly tothe hot metallic surface. No excess powder remained on the surface.

The moisture vapor permeability (ASTM Test D-988- 1T) of a metalizedpaper prepared as above described was 2.7 grams per 24 hours per 100 sq.in. at 100 F. and 90% relative humidity. Creasing of this sheet at 70 F.and 50% relative humidity prior to testing it increased the permeabilityonly to 4.5 grams.

Metalized paper prepared in accordance with this example is particularlywell suited for decorative wrappings and packaging in general because ofthe good toughness and flexibility of the low-molecular weightpolyethylene.

Example 2 A sheet coated with a thin film of the polyethylene of Example1 was prepared as in that example and a 325- mesh aluminum leafingpigment dusted on. The dusted sheet was heated for one minute at 400 F.

Other powders or particulate matter which have been successfully appliedby this means include, but are not limited to, a bright zinc flake, abronze powder, copper powder, ultramarine blue pigments, and a mixtureof 85% by weight 325-mesh aluminum powder and a 15% finely dividedultramarine blue. Many pigments and substantially any decorativemetallic powder can be applied by this means to obtain a variety ofattractive colors and surface textures. While pigments such asultramarine blue can be applied, better surface appearance is obtainedby mixing such pigments with metallic powders, preferably aluminumpowder. It is also, of course, within the scope of this invention toachieve coloring by using a colored film as the thermoplastic binder.

In the case of the low-molecular Weight polyethylene of Example 1, whichhas been found to be one of the preferred film-forming thermoplastics,it has been found preferable to further achieve a highly glossy filmsurface by drawing the film coated surface while the polyethylene isstill molten, under tension across a surfacing bar prior to dusting thepowders thereon to further improve the surface appearance of thefinished article. For enhancing brilliance, the surface of this bar orroll can be smooth and polished or it can be striated or otherwisealtered to impart a design to the coating. For example, a surfacing barwound with fine metal wire has been found to apply an attractive ribbedappearance to the finished article.

Example 3 A mixture of 90 parts by weight of the low-molecular weightpolyethylene of Example 1 and parts by weight of a terpene resin(Piccolyte S1l5 of the Pennsylvania Industrial Chemicals Corp.) servingas a tackifier was roll-coated at 325 F. on a' 35-ponnd paper pouchstock followed by rapid chilling. Polished aluminum powder (325-mesh)was then applied by brushing onto the coated face and the compositeheated at 300 F. for one minute. The small quantity of tackifierpermitted the metallic powder to be more easily adhered to the binderfilm at lower temperatures.

Other modifying materials can be added to the low molecular weightpolyethylene to modify its properties provided that the resultingviscosity at 300 F. is not reduced below 1000 and preferably not below3000 centipoises. For example, 0.5% by Weight of a high-molecular weightaliphatic amide (for example, Armid O of Armour & Co.) can beincorporated in the coating of Example 3 above to provide a morebrilliant metallic finish on the product. A small quantity of a parafiinwax may also be added to the polyethylene to reduce its cost and tosomewhat reduce its viscosity.

Example 4 A medium-molecular weight polyethylene resin (sold by E. I. duPont de Nemours and Company, Inc., as Alathon 18) was extrusionlaminated to a board stock support to a coating thickness of 1 mil. Thispolyethylene can be further characterized as having a melt index of 24.5as determined by ASTM Test D-238-52T. Its viscosity, even at 300 F., wasso high that it could not accurately be measured.

After cooling, the plastic surface was dusted with 325- mesh aluminumpowder and then heated by a blast of hot air at 450 F. for aboutone-half minute. This higher temperature was required for good bondingsince the molecular weight and melt viscosity of this polyethylene arehigher than the polyethylene of Example 1. A higher molecular weightpolyethylene having a melt index of 3 was used in place of the mediummolecular weight material and heating by hot air blast at 550 F. forabout one-half minute was required to render the film surfacesufficiently tacky to firmly attach the aluminum powder.

Example 5 A polyamide resin having a viscosity of 3,700 centipoises at300 F. and a tensile strength of 1000 p.s.i. was knife coated at 350 F.onto a 55-pound highly calendered glossy paper (ream basis, 3000 sq.ft.) to a coating thickness of 1 mil. This polyamide is commericallyavailable from General Mills, *lnc, as Versamid 940. Aluminum powder of325-mesh was dusted onto the coating surface, the excess removed, andthe sheet thereafter heated for one minute at 350 F. to bond the metalto the resin. The same resin was also dissolved (40% solids) in equalparts of isopropanol and toluene and reverse roll coated onto a highlycalendered paper stock weighing 40 pounds per 3000 sq. ft. The coatingwas dried in an oven with a resulting coating 0.2 mil in thickness,dusted with the same aluminum powder and heated in a circulating airoven at 300 F. for one minute.

Example 6 A butadiene-styrene copolymer (sold by Pennsylvania IndustrialChemical Corp. as Piccoflex having a viscosity in excess of 100,000centipoises at 300 F. and a tensile strength of 500 p.s.i., wasreverse-roll coated from a 50% solids solution in toluene onto the paperstock of Example 5 to a coating thickness of 0.15 mil. The film was thendried in an oven and thereafter dusted with a fine bronze powder. Thedusted sheet was heated for one minute at 300 F. and subsequentlycooled.

By any of the foregoing examples, an attractive firmly bonded metallicsheet, particularly desirable for use as a packaging material, can beproduced economically and with a variety of surface appearances andcolors. However, any article on which it is feasible to deposit a glossyfilm of a thermoplastic material of the type defined can likewise begiven a metalized surface.

Where paper or other flexible membrane comprises the support, very highproduction speeds are possible, for example, linear treating speeds from200 to 800 feet per minute may be employed. The amount of metallicpowder or particulate matter applied may be varied; and in general lowpowder pick-up results in greatest gloss while the higher powderpick-ups result in rich, deep but duller matte finishes which,particularly in the case of aluminized surfaces, afford a good thermalbarrier.

It will be seen from the description of the product and process of thisinvention that it is possible to form novel and useful metalizedarticles. Moreover the process is simple, it permits variations withoutadditional steps and achieves the metalizing of a surface with a minimumquantity of metallic powder. Moreover, the articles formed have a widevariety of applications. For example, the metalized papers, somecontaining as little as metal coverage, are extremely pleasing to theeye and offer wide applications in decorative wrapping papers. Moreover,such metalized papers may be formed in many variations, such as smoothsurface, rippled surface and the like. When the metallic powder isapplied in heavier quantities, i.e., up to the point where 100% of thesurface is covered with metallic powder, an article may be made withexhibits very high thermal insulation characteristics.

By means of this invention, the defects of the prior art products andprocesses are overcome and an attractive decorative product is providedwhich is substantially less expensive than foil laminate orvacuum-deposited surfaces. The metallic powder is so Well bonded to thethermoplastic film surface that there is no substantial ruboff orscratch removal of pigment in ordinary usage. As an example of thisexcellent bond, pressure-sensitive tape, such as Scotch brand tape, canbe adhered to the metal surface and stripped therefrom without anysubstantial removal of particulate matter. In addition to theirattractive appearance, products according to this invention may possessother desirable properties such as low vapor transmission and may beheat-sealable which makes them very desirable as packaging materials.

It should be understood that the foregoing description is for thepurpose of illustration only and that this invention includes allmodifications falling within the scope of the appended claims.

I claim: 1

1. The method of coating the surface of an article with particulatematter, said surface comprising a glossy thermoplastic material having aBrookfield viscosity of at least 1,000 centipoises at 300 R, whichcomprises as steps applying to said surface while in its normal nontackysolid condition finely divided particulate matter to the extent thatbetween about 10 and 100% of said surface is substantially uniformlycovered with said particulate matter, thereafter converting said surfaceby heat to a highly viscous liquid supporting said particulate matter insubstantially the outer surface thereof, and reconverting said surfacewith cooling to said normal non-tacky solid condition whereby saidmatter is supported by said surface and firmly bonded thereto to producea highly attractive surface.

2. Method in accordance with claim 1 wherein said 10 finely dividedparticulate matter is metallic powder substantially all of which issized no larger than 325-mesh.

3. Article formed by the method of claim 1 and characterized by aparticulate coating present in a quantity not greater than about 1.5pounds per 3,000 square feet of said surface.

4. The method of coating the surface of an article comprising the stepsof applying to said surface a substantially continuous glossy film of athermoplastic material having a Brookfield viscosity of at least 1,000centipoises at 300 F., applying to said film while in its normal,non-tacky solid condition finely divided particulate matter sufficientto substantially uniformly cover between about 10 and of the surface ofsaid film, converting said surface of said film by heat to a highlyviscous liquid supporting said particulate matter in substantially theouter surface thereof, and reconverting said surface with cooling tosaid normal non-tacky solid condition whereby said matter is supportedby said surface and firmly bonded thereto to produce an attractivesurface.

5. Method in accordance with claim 4 wherein said thermoplastic materialhas a Brookfield viscosity of at least 3,000 centipoises at 300 F. andis further characterized as having a tensile strength of .at least 100p.s.i.

6. Method in accordance with claim 4 wherein said thermoplastic materialis polyethylene.

7. Method in accordance With claim 4 further characterized by the stepof imparting a decorative design to said thermoplastic film.

8. Method in accordance with claim 4 wherein said applying saidthermoplastic material to said surface is accomplished by hot meltcoating and further characterized by drawing said thermoplastic filmunder tension across a surfacing bar during said coating.

9. Method in accordance with claim 4 wherein reconverting said surfacecomprises the step of rapidly chilling said film.

References Cited in the file of this patent UNITED STATES PATENTS2,041,297 Moore May 19, 1936 2,332,221 Harshberger Oct. 19, 19432,479,094 Bicknell Aug. 16, 1949 2,632,205 Fitz Harris Mar. 24, 19532,920,947 Burk et al Jan. 12, 1960 2,955,958 Brown Oct. 11, 1960 FOREIGNPATENTS 223,529 Great Britain Nov. 13, 1924 601,713 Great Britain May11, 1948 775,371 Great Britain May 22, 1957

1. THE METHOD OF COATING THE SURFACE OF AN ARTICLE WITH PARTICULATEMATTER, SAID SURFACE COMPRISING A GLOSSY THERMOPLASTIC MATERIAL HAVING ABROOKFIELD VISCOSITY OF AT LEAST 1,000 CENTIPOISES AT 300*F., WHICHCOMPRISES AS STEPS APPLYING TO SAID SURFACE WHILE IN ITS NORMAL NONTACKYSOLID CONDITION FINELY DIVIDED PARTICULATE MATTER TO THE EXTEND THATBETWEEN ABOUT 10 AND 100% OF SAID SURFACE IS SUBSTANTIALLY UNIFORMLYCOVERED WITH SAID PARTICULATE MATTER, THEREAFTER CONVERTING SAID SURFACEBY HEAT TO A HIGHLY VISCOUS LIQUID SUPPORTING SAID PARTICULATE MATTER INSUBSTANTIALLY THE OUTER SURFACE THEREOF, AND RECONVERTING SAID SURFACEWITH COOLING TO SAID NORMAL NON-TACKY SOLID CONDITION WHEREBY SAIDMATTER IS SUPPORTED BY SAID SURFACE AND FIRMLY BONDED THERETO PROUDCE AHIGHLY ATTRACTIVE SURFACE.
 2. METHOD IN ACCORDANCE WITH CLAIM 1 WHEREINSAID FINELY DIVIDED PARTICULATE MATTER IS METALLIC POWDER SUBSTANTIALLYALL OF WHICH IS SIZED NO LARGER THAN 325-MESH.